Magneto-resistive effects include a number of different physical phenomena, all of which having in common that an electrical resistance of a resistive element is alterable by the behavior of a magnetic field penetrating the resistive element. Technologies utilizing magneto-resistive effects are sometimes referred to as “xMR technologies”, whereby the “x” indicates that a multitude of effects may be addressed here, like the Giant Magneto-Resistive (GMR) effect, the Tunnel Magneto-Resistive (TMR) effect, or the Anisotropic Magneto-Resistive (AMR) effect, to mention just a few examples. xMR effects may be applied in a variety of field-based sensors, for example for measuring revolution, angles, etc. In some applications, especially in applications relevant to safety, it is required that these sensors operate reliably and at a high level of accuracy.
A sensor may, in some applications, be subject to perturbations in the form of unknown or incalculable magnetic fields. These perturbations may randomly change a state or an initial value of the sensor. Since hysteresis behavior of the sensor may result in a substantial difference whether a measured value is approached from an initial value above or below the measured value, hysteresis may lead to an error in measurement results. A magnetic xMR sensor concept with a free layer in a vortex configuration (closed flux magnetization pattern) may have nearly zero hysteresis. Low hysteresis may in other words be achieved in the presence of a vortex shaped magnetization state (magnetic field) in the free layer, and may especially be interesting in applications such as wheel speed sensing, current sensing, or linear field sensing. The vortex shaped magnetization state, however, may only be stable in a certain range regarding field strength of the applied field to be measured.
It is hence desirable to provide a sensor element enabling improved accuracy and reliability of measurement results.